<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<!-- 1.准备好一个“容器” -->
<div id="test"></div>
<!-- 引入react核心库 -->
<script src="../js/17.0.1/react.development.js"></script>
<!-- 引入react-dom。用于支持react操作DOM -->
<script src="../js/17.0.1/react-dom.development.js"></script>
<!-- 引入babel，用于将jsx转为js -->
<script src="../js/17.0.1/babel.min.js"></script>
<script type="text/babel">
    //创建组件
    class Count extends React.Component {
        //构造器
        constructor(props) {
            console.log("Count--constructor");
            super(props);
            //初始化状态
            this.state = {
                count: 0
            };
        }


        //加1按钮的回调
        add = () => {
            //获取原状态
            const {count} = this.state;
            //更新状态
            this.setState({count: count + 1});
        };

        //卸载组件按钮的回调
        death = () => {
            ReactDOM.unmountComponentAtNode(document.getElementById("test"));
        };
        //强制更新按钮的回调,不受阀门开关的影响
        force = () => {
            //
            this.forceUpdate();
        };
        //若state的值在任何时候都取决与props，那么可以使用getDerivedStateFromProps
    static getDerivedStateFromProps(props,state){
        console.log('getDerivedStateFromProps',props,state);
        //必须返回状态对象or null
        return null
        // return props
    }
        //在更新之前获取快照
        getSnapshotBeforeUpdate(){
            console.log('getSnapshotBeforeUpdate');
            //任何值都可以当成快照值，会传递给componentDidUpdate
            return 'aaa'
            // return null
        }
        //组件将要卸载的钩子
        componentWillUnmount() {
            console.log("Count---componentWillUnmount");
        }

        //组件挂载完毕的钩子
        componentDidMount() {
            console.log("Count---componentDidMount");
        }

        //控制组件更新的阀门
        shouldComponentUpdate() {
            console.log("Count---shouldComponentUpdate");
            return true;
        }

        //组件更新完毕的钩子
        componentDidUpdate(preProps,preState,snapshotValue) {
            console.log("Count---componentDidUpdate",preProps,preState,snapshotValue);
        }

        render() {
            console.log("Count---render");
            const {count} = this.state;
            return (
                <div>
                    <h2>当前求和为:{this.state.count}</h2>
                    <button onClick={this.add}>点我+1</button>
                    <button onClick={this.death}>卸载组件</button>
                    <button onClick={this.force}>不更改任何状态中的数据，强制刷新</button>

                </div>
            );
        }
    }
    //渲染组件
    ReactDOM.render(<Count count={199}/>, document.getElementById("test"));
</script>
</body>
</html>